There has been widely employed an electrostatic chuck that electro-statically attracts and holds a sample such as a wafer or a glass in a device that is used in a semiconductor manufacturing process required in forming an integrated circuit on a semiconductor wafer such as silicon, such as an etching device, a plasma processing device used for formation of a thin film through a chemical vapor deposition (abbreviated to CVD), an electron exposure device, an ion rendering device, an ion implanting device, or in a device that is used in a process of manufacturing a liquid crystal display panel which is employed for a TV screen or a computer display such as a substrate bonding device or an ion doping device which is used in press-inserting liquid crystal in an insulating substrate such as a glass. This is because the electrostatic chuck exercises an excellent performance with respect to a problem of a damage of a sample, a problem of a high defect rate that is attributable to particles which are generated from a scratch caused by a mechanical contact, the compensation of the flatness of the held sample, and the like as compared with holding using a mechanical mechanism.
In recent years, large size liquid crystal display televisions have been widely used, and flat panel displays have been developed. In response, there is the necessity of processing larger glass substrates than the past glass substrates. As an example, products using large substrates that exceed 1 m×1 m in size have been manufactured. Also, in a semiconductor manufacturing process, processing of a silicon wafer that is 300 mm in diameter is becoming a present mainstream. In both cases, the size of products is becoming larger, and an increase in the weight of the glass substrate and the semiconductor wafer makes more important the high attracting performance as well as the flatness of the sample on an attracting plane when the sample is attracted by the electrostatic chuck.
In general, the flatness of the sample that has been attracted by the electrostatic chuck on the attracting plane is associated with the magnitude of a holding force by which the electrostatic chuck holds the sample. In other words, as the sample to be attracted is increasing in size as described above, the electrostatic chuck must have the sufficient holding force.
In the bipolar electrostatic chuck that applies positive and negative voltages to two electrodes, it is presumed that a semiconductor wafer such as silicon or dielectric material such as a glass substrate is attracted by the action of a gradient force F that is developed in the case of an uneven electric field as expressed by the following Formula (1). The gradient force is proportional to the spatial differential of the electric field intensity E squared, that is, the gradient.F∝∇(E2)  (1)
Up to now, there have been reported several bipolar electrostatic chucks that allows a distance between the adjacent electrodes to be narrowed. For example, there has been reported a bipolar electrostatic chuck in which electrodes each having a band-like comb teeth configuration are alternately arranged to form a one-layer comb type bipolar electrode of 10 cm×10 cm, and the respective electrodes are arranged at a pitch of 1 mm (each of the electrode widths is 1 mm and the interval between the respective electrodes is 1 mm), and a surface dielectric layer is set to 50 μm (see K. Asano, F. Hatakeyama, and K. Yatsuzuka, “Fundamental Study of an Electrostatic Chuck for Silicon Wafer Handling”, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting (Cat. No. 97CH36096), Part: vol. 3, Pages: 1998-2003). The electrostatic chuck obtains an attracting performance of equal to or less than 3N at a supply voltage of 1500 V with respect to a silicon wafer to be attracted. This corresponds to equal to or less than 3 fg/cm2 in the terms of an attracting performance per unit area. Also, there has been reported an example in which the line width of the band-like electrodes and the interval of the band-like electrodes are set to 0.3 to 3 mm, respectively, in a bipolar electrostatic chuck having a pair of band-like electrodes in the interior of an insulating material (see JP 10-223742 A). In addition, there has been reported an example in which electrodes apart from each other are disposed on a dielectric base, and the electrode width and the electrode interval of those electrodes are set to 100 μm or less, respectively (see JP 2000-502509 A).
However, in the case where the distance between the electrodes that are adjacent to each other is shortened, there arises a problem of a discharge limit. That is, because it is difficult to control an etching cross-section of an electrode material that is used for the electrostatic chuck and to control the formation of an adhesive layer that fixes the electrodes in the interior of the insulating material, for example, as expressed in a schematic cross-sectional view (enlarged view) of the vicinity of the electrodes shown in FIG. 28 that illustrates a cross section of the conventional bipolar electrostatic chuck, an electric field is liable to be concentrated to sharp portions of edges of a first electrode 2 and a second electrode 4 which are attributable to uneven etching. Also, voids occur when an adhesive agent for forming an adhesive layer that fixes the respective insulating layers to each other or the insulating layers with the electrodes is bonded. As a result, the dielectric breakdown strength is remarkably deteriorated between the adjacent electrodes. For that reason, in the above-mentioned bipolar electrostatic chuck, when a distance between the electrodes is close to a given distance, there is an uncertainty that a discharge may occur between the electrodes.
In general, it is presumed that the discharge limit is about 3 kV when the distance between the electrodes is 0.5 mm in the bipolar electrostatic chuck. In fact, in the case of using the bipolar electrostatic chuck described above, a voltage that is lower than this discharge limit must be applied from the viewpoint of the safety ratio. For that reason, in the conventional bipolar electrostatic chuck that narrows the interval between the electrodes as described above, a voltage that can be actually applied is limited, and there arises such a problem that a sufficient attracting performance, i.e., gradient force, cannot be exercised because a weight per unit area is increased with respect to a semiconductor wafer that is increasingly enlarged diameter in size or a glass substrate that is used for a liquid crystal TV or a flat panel display which are increasingly enlarged in size.
On the other hand, in the case where an insulating sample is attracted by the electrostatic chuck, there arises such a problem that a sample is difficult to dismount from the attracting plane of the sample due to the residual charges even if a voltage that is applied to the electrodes is turned off. In particular, this problem becomes severe as the sample is increasingly enlarged in size.
The electrodes are positioned in a plane in most of the bipolar electrostatic chucks including the type described above. There has also been reported an electrostatic chuck of the type in which a plurality of electrodes are laminated on one another in the interior of the insulating material (see JP 2838810 B). This bipolar electrostatic chuck is identical with the above-mentioned bipolar electrostatic chuck in the viewpoint that electrodes that are different in the polarity positioned in the same plane, and suffers from the discharge limit likewise.    Patent Document 1: JP 10-223742 A    Patent Document 2: JP 2000-502509 A    Patent Document 3: JP 2838810 B    Non Patent Document 1: K. Asano, F. Hatakeyama, and K. Yatsuzaka, “Fundamental Study of an Electrostatic Chuck for Silicon Wafer Handling”, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference thirty-second IAS Annual Meeting (Cat. No. 97CH36096), Part: vol. 3, Pages: 1998-2003